To the Norsemen, the Japanese, and the Carthaginians; to the Irish, the Africans, and a long list of others who, it is claimed, crossed the oceans to America long before 1492, add one more: the Chinese.

They toured up and down both coasts of the Americas, established colonies, made maps, and left behind chickens. That, at least, is the theory posed by former British naval officer and amateur historian Gavin Menzies.

What is surprising is not so much the claims themselves but the buzz they've created in popular culture both here and in Britain - especially given that few professionals in the field find his case convincing.

Mr. Menzies's book, "1421: The Year China Discovered America," has sold more than 75,000 copies since it hit British shelves in October. It debuted in the US at No. 8 on the New York Times bestseller list earlier this month. Mr. Menzies, who reportedly received an $800,000 advance from Bantam, has appeared on TV and radio. He's been profiled in the New York Times magazine. A PBS documentary is close behind.

"He's come up with a story people want to believe in," marvels Gillian Hutchinson, curator of cartography at London's National Maritime Museum who heard Menzies give a lecture last spring at the Royal Geographic Society. "There was almost a religious fervor in the audience."

This isn't the first time a tale of preColumbian discovery has captured the popular imagination. Thor Heyerdahl's 1950 book "Kon-Tiki" claimed that ancient Peruvians crossed the Pacific by raft - and documented his own attempt to emulate them. Then there was Harvard marine biologist Barry Fell, who translated scratches on rocks as ogham script, claiming evidence of Asian, African, and Celtic exploration. And many an Irishman insists the first person to reach America was none other than Brendan the Navigator, a 6th-century Irish monk.

Before Christopher Columbus was born

But Menzies's tale, which looks at a well-documented voyage by a Ming Dynasty fleet in 1421, is more specific in its assertions than most theories. In his version, a fleet led by admiral Zheng He rounded the Cape of Good Hope and then split up. One group explored South America, Antarctica, and Australia, while other ships toured Central and North America, circled Greenland, learned to measure longitude, and established settlements. Menzies says all records of the voyages were later destroyed.

For evidence of his theory, Menzies casts a broad net, citing shipwrecks, anchor stones, language, and maps that he says helped guide Columbus and Magellan. The historian points to a map the Portuguese had by 1428 that suggested some Caribbean islands long before any European was known to have traveled there. Menzies believes the chart was derived from Chinese explorations.

The book is more detective novel than history, with Menzies as the Hercule Poirot who pieces together the clues, helped by his navigation experience. "If I have found information that escaped [eminent historians]," he writes, "it is only because I knew how to interpret the extraordinary maps."

There's just one problem: Mainstream historians consider the book hogwash.

"It's absolutely preposterous," laughs Donald Blakeslee, an archeologist at Wichita State University in Kansas, referring to one of the book's claims: that ships with "gilded sterns" had sailed up the Mississippi River and into the Missouri. "A seagoing vessel couldn't have gotten close to that area."

Dennis Reinhartz, who teaches the history of cartography at the University of Texas at Arlington and is a past president of the Society for the History of Discoveries, agrees. "There's a whole genre of this stuff," he says with a laugh. "People are forever saying this line [on a map] represents this or that ... but it's still shaping a square peg to fit a round hole." Much of the evidence Menzies points to - a mysterious tower in Newport, R.I., for instance, and several 15th-century maps - has been used to support other theories.

None of this, however, takes away from the charm of the author or his story. Read it, or better yet, listen to Menzies for a few minutes, and it's hard to resist his enthusiasm. Charismatic, with a delightful British accent, he sounds like a kid who's just worked out the solution to a particularly tricky riddle.

"There's a flood of new evidence," he exclaims, ticking off a list of clues of Chinese settlements in America.

"So, for New York, the first person who got there was Giovanni de Verrazzano, and in trying to find the Northwest Passage he met people he described as Chinese! In Florida, Pedro Menendez de Aviles found wrecks of Chinese junks in the Atlantic. In Peru, Friar Antonio de la Calancha found pictures people had painted of the Chinese cavalry...." He keeps going, enthusiasm unabated.

Unconventional theories

That exuberance may account for some of the book's popularity. "It's a delightful read," says Nancy Yaw Davis, an independent scholar in Anchorage, Alaska. Dr. Davis understands what it's like to have academics attack a pet theory. Most dismissed her book, "The Zuni Enigma," which described the influence of 13th-century Japanese explorers on Zuni Indians. Though disappointed in some of his evidence, Davis admires Menzies.

"He was gutsy," she says, adding, "I was a wee tad envious. I had hoped my book would generate that kind of recognition."

What is it about discovery theories that can so capture the imagination? "It's about rewriting history," says John Steele, an executive producer of the upcoming PBS documentary, "1421: The Year China Discovered the World." Menzies upends Captain Cook's claim to Australia and Magellan's claim to the first circumnavigation, he notes. "But the thing that really gets everyone is discovering America before Columbus."

The Italian-American community, perhaps the fiercest defender of Columbus's legacy, is used to such challenges. "Every nationality claims to have a Columbus," says Adolfo Caso, author and founder of the Internet-based Dante University. "Regardless of who may have been here before or after, the Europeans met the Indians because of Columbus," he says firmly.

If Menzies is correct - what to do about that well-known rhyme? A visitor to his website, www.1421.tv, offers one suggestion:

"In fourteen hundred twenty-one

China sailed there before anyone."

Just don't look for fifth-graders to be memorizing the couplet anytime soon.